1. Field of the Invention
The present invention generally relates to a typewriter which may be simply and inexpensively fabricated and assembled for portable use. More specifically, the present invention relates to an improved ribbon switching mechanism for a typewriter.
2. Description of the Prior Art
In prior typewriters, a ribbon switching device is provided to allow use of a two color ribbon. When a lower color section of the two color ribbon is used, the ribbon is shifted up by the ribbon switching device. One typical conventional ribbon switching device is schematically illustrated in FIG. 1, which shows the device in the position to use the lower portion of the ribbon. When a ribbon switching key 1 is moved in the direction of arrow A, this action is transmitted by a link 2 to a crank 3. Rotation, thus, of the crank 3 in a counterclockwise direction as seen in the figure moves the end of a link 4 engaging in a T-shaped slot in a crank 5 toward the left side of the T-shaped slot. When a key is pressed to type a character, the link 4 is pulled downward in the diagram and by engaging with the T-shaped slot in the crank 5, rotates the crank 5 counterclockwise as shown in the figure, whereby the linkage consisting of a link 6, crank 7 and ribbon holder 8 is activated to raise the ribbon. It will be seen that switching the link 4 between left and right hand ends of the T-shaped slot in the crank 5, the leverage provided by the crank 5 is adjusted so that the type hammers hit either the upper or lower portion of the ribbon according as the link 4 is at the left or right hand side respectively of the T-shaped slot. Since a portable typewriter is manufactured to be compact, it is necessary to reduce its weight and number of parts. Such a conventional ribbon switching device, however, comprises many parts, many of which are made of metal except for the switching key, thereby increasing weight and cost.